1. Related Applications
This application claims priority from GB 9412809.7, filed Jun. 25, 1994.
This application is related to U.S. Ser. No. 08/425,021, entitled ENGAGEMENT FAULT DEGRADED MODE CONTROL, now U.S. Pat. No. 5,539,894, filed the same date, Apr. 19, 1995, and assigned to the same assignee, EATON CORPORATION, as is this application.
2. Field of Invention
The present invention relates to a control method and control system for shifting a compound semi-blocked, splitter-type automatic or semi-automatic transmission system. Automatic and semi-automatic mechanical transmission systems are known in the prior art and illustrated in U.S. Pat. Nos. 4,361,060 and 4,648,290, the disclosures of which are hereby incorporated by reference. Semi-blocked compound transmissions of the splitter type are known in the prior art and illustrated in U.S. Pat. Nos. 3,924,484; 4,735,109 and 4,736,643, the disclosures of which are hereby incorporated by reference.
In particular, the present invention relates to a shift control method/system for an automated compound semi-blocked mechanical transmission system wherein, upon sensing that the main section is engaged in the desired ratio thereof and that a known ratio has not engaged, the initial recovery response is a sequence of operations undertaken to cause a blocked splitter clutch assembly to unblock, allowing engagement of the splitter section ratio associated with the target ratio. If the initial response does not successfully cause engagement of the target ratio, then other fault detection and degraded mode routines are undertaken.
3. Description of the Prior Art
Fully automatic transmission systems, both for heavy-duty vehicles such as heavy-duty trucks and/or coaches, and for automobiles, that sense throttle openings or positions, vehicle speeds, engine speeds, and the like, and automatically shift the vehicle transmission in accordance therewith are well known in the prior art. Such fully automatic change gear automated mechanical transmissions utilizing electronic and/or pneumatic logic and actuators to engage and disengage mechanical (i.e., positive) clutches to achieve a desired gear ratio. Examples of such transmissions may be seen by reference to U.S. Pat. Nos. 3,961,546; 4,081,065; 4,361,060; 4,569,255; 4,576,065; 4,595,986; and 4,576,263, the disclosures of which are hereby incorporated by reference.
Semi-automatic mechanical transmission controls wherein automatic changing between a plurality of gear ratios is provided while normally permitting the driver to choose when to make a particular gear ratio change, whether to select the immediately consecutive ratio up or down or to skip one or more ratios, and when to slip (i.e., to incompletely engage) the vehicle master clutch in a lower crawler gear, are known. Furthermore, the semi-automatic control system prohibits engagement of a driver-selected higher ratio (i.e., an upshift) that would cause the engine speed to decrease below the idle speed (i.e., would cause stalling and/or over-stressing at low speeds of the engine) and of a lower ratio (i.e., a downshift) if such a change would cause overspeeding of the engine. Examples of such a semi-automatic transmission control can be seen by reference to above-mentioned U.S. Pat. No. 4,648,290.
A control method for shifting automatic and semi-automatic mechanical transmissions (called "AMTs") including semi-blocked, splitter-type compound transmissions wherein each shift, both simple (auxiliary section only) and compound (main and auxiliary section), involves shifting of the main transmission section to neutral to allow shifting of the blocked auxiliary section without requiring a crossing of synchronous of the preselected jaw clutch members, is disclosed in U.S. Pat. No. RE 32,591, the disclosure of which is hereby incorporated by reference.
While the aforementioned, automatic, semi-blocked transmission systems and controls therefor are generally satisfactory, in certain situations, the target gear ratio did not engage and, thus, it is desirable to provide an engagement fault detection technique and a fault recovery mode and/or fault degraded mode of operation.